Open cell foams, such as melamine resin foams, are lightweight and have thermal and acoustic properties that render such foams attractive as insulation materials in commercial aircraft applications. Furthermore, open cell foam insulation materials may be easier to install than traditional fiberglass insulation materials and, therefore, may potentially reduce overall manufacturing costs.
However, thermal and acoustic insulation materials used in commercial aircraft applications are subject to governmental regulations regarding flammability. In particular, various government regulations require testing for radiant panel flammability, vertical burn, combustion toxic gas generation and combustion smoke generation. For example, the radiant panel test requires that insulation materials, alone or, more typically, covered in protective films, be subjected to a directed on surface propane pilot flame for 15 seconds, while being under an intense radiant heat source that measures 1.7 Watts/cm2 at the zero point. Under these conditions, the insulation material must resist propagating a flame greater than 2 inches, nearly an inch of which typically occurs as an artifact of the flame's initial strike on the surface. In addition, any after-flame on the material must self-extinguish within 3 seconds.
As will be appreciated by those skilled in the art, passing such stringent flammability tests on a consistent, long term basis has proven difficult for typical foam insulation materials. Therefore, aircraft manufacturers have continued to use traditional mineral-based insulation materials.
Nonetheless, those skilled in the art continue to seek materials, including foam materials, capable of meeting rigorous flammability requirements.